This chapter summarizes the evidence documenting the effects of food prices and income on body weight. The general theme of compensating behavior recurs in the study of food-price changes and body weight. There are a number of possible approaches to identification, but all suffer from one or more key weaknesses. Nonetheless, the collage of evidence pieced together from different identification strategies can still be informative. The literature finds evidence that while higher prices of fast food depress body weight, higher prices for fruit and vegetables may have the opposite effect. It is suggested that income may not play an independent causal role in childhood weight, above and beyond the usual suite of socioeconomic characteristics. There is a theoretical prediction of the competition between the demand for healthy body weight, which rises with income, and the demand for food, which also rises with income.